Hard tantalum and method of hardening



Sept- 24, 1935 M. M. AUSTIN 2,615,509

HARD TAN-TALUM AND METHOD OF HARDENING Filed Feb. 28, 1951 w E y Patented Sept. 24, 1935 UNITED STATES PATENT OFFICE A 2,015,509` y d HARD TANTALUM AND METHOD 0F nAnDENTNG Y l Application February 28, 1931, Serial No. 519,177 Y 10 Claims. (Cl. 148-16) This invention relates in general to hardened metals and has more particular reference to hardened tantalum and a method of hardening atmosphere to harden the refractory metal and to control such hardening by controlling `theabsorption of the air by the refractory metal.

A further important object of the invention is the provision of case hardened tantalum and tantalum articles, and a novel method of producing such tantalum or articles having the desired hardness.

Other objects and advantages ofthe invention will be apparent from the following description and from the accompanying drawing, in which similar characters of reference indicate similar parts throughout the several views.

In the drawing Fig. 1 is adiagrammatic view of apparatus suitable for treating `the refractory metal and articles thereof in accordance with the invention; and

Fig. 2 is a transverse sectional view of a heating element suitable for use in my novel method and showing a refractory metal in place for the quality and will consequently cause a pecuniary loss when sold.

Other uses of a hard, non-corrosive and durable metal will be apparent, the foregoing embodiment being recited merely by way of example. For instance, turbine blades, chemical and electro-chemical apparatus, and other heavy duty articles which in their use are subject to wear or corrosive atmospheres.

The properties of tantalum have already caused this material to be a favorite for such uses, but

in many i'nstances, it is desirable to have a material with the non-corrosive or acid resisting and hard qualities voi' tantalum, together with a greater degree of hardness, durability or wear resisting qualities' and workability. l

It has been suggested to provide a material harder than tantalum and with some of its properties, by alloying tantalum with a harder material, such as tungsten, and by alternately heating andhammering tantalum. The tantalum-tungl0 sten alloy is objectionable for such uses, because the degree of hardness is not readily controllable, and the resulting properties of such an alloy are not altogether desirable. Moreover, such an alloy is expensive to produce, and does not possess 16 the degree of hardness required for such uses, and is not readily workable.

It is conceivable that the method of alternately heating and hammering tantalum might produce hardened tantalum, but such a method does not 20 readily adapt itself to controlledly hardening tantalum, and must be painstakingly vcarried out, the method being highly impractical and subject to many other limitations.

By an exhaustive study of the properties of tantalum and by the application of prior art methods of hardening other metals, three methods readily suggest themselves as being practical and possibly successful. yThese three methods are heating the tantalum in air at atmospheric pressure, heating and quenching the tantalum, and heating tantalum in an atmosphere of a gas which tends to combine with tantalum to produce a hard composition.

I have tried these three methods and found that no useful hardness of tantalum can thereby be obtained, but that a vigorous reaction occurs at the surface ofthe tantalum and very little penetration of gases to the interior of the tantalum results. Moreover, such methods result in discoloration and rotten metal.

Briefly, the present invention contemplates a novel method for overcoming the foregoing objections and producing tantalum or articles, having a varying degree of hardness from the outer surface inwardly, a degree of hardness uniformly distributed throughout the section of the tantalum or tantalum article, or a hardened case on the tantalum or an article made therefrom. In order to accomplish the foregoing objects, I heat tantalum or tantalum objects in a reduced pressure, to a temperature at which the gases occluded by the metal are freed, and separate or pump such gases from the container in which the tantalum is heated. 'I'his degasied tantalum is 55 maintained at the degasication temperature in a reduced pressure and measured quantities of air` are successively admitted to the tantalum heated in a reduced pressure, and are absorbed '5 uniformlyby the surface of the tantalum. Further lheating of the tantalum carrying at its surface this absorbed air, operates to diffuse the air in the body of the material and to diil'use or distribute, as it were, the hardness oi the material from the surface inwardly thereof. The degree of hardness is apparently determined by the amount or quantity of air absorbed by the tantalum or tantalum article, and the diffusion of the air throughout the tantalum body and the degree of hardness may therefore be controlled by the amount or quantity of air admitted to the tantalum heated in a reduced pressure, and the control of the time during which the tantalum is heated. r It will of course be apparent thata hardened case may be formed on the tantalum or tantalum articles by admitting the desired amount of air and continuing the heating of the tantalum until I the air is absorbed by the surface of the tantalum, and this hardness may be made to vary from the surface of the tantalum body inwardly thereof until the air is uniformly distributed throughout the` section, at which time the material is uniformly hard, by controlling the time during which the tantalum is heated.

While I do not wish to limit my invention to any particular apparatus for accomplishing the novel results, I have illustrated by way of example in the drawing, suitable devices for hardening tantalum. 'Ihis apparatus comprises any suitable heating unit or furnace capable of developing .the desired temperatures and of `providing a heating vacuum chamber, such, for example as a quartz tube 5, closed at each end by means of rubber Stoppers or caps 6 and provided with a source of heat which I have illustrated as an external coil 'I encircling the quartz tube 5 and connected by means of conductors 8 to a suitable source of electrical potential, not shown. The electrical energy supplied to the coil I may be controlled by any suitable switch 9, as shown in the drawing.

A frame, receptacle, or holder I I of any suitable metal capable of withstanding the temperature developed within the quartz tube 5, is provided for carrying the tantalum or tantalum articles to be treated. This holder or receptacle I I is preferably of tantalum or any other suitable highmelting point metal or alloy and` is illustrated as a `cylinder carrying tantalum strips or articles I2, as shown in Fig. 2, or the tantalum cylinder may be provided with a plurality of apertures I3 as shown in Fig. 1 for carrying a plurality of spinnerets or other tantalum articles I4. This holder or receptacle carrying the tantalum or articles to be hardened, is inserted in the tube 5 and may be Supported therein by any suitable means, such as brackets I5 at each end of the tantalum receptacle. Where: the Stoppers or caps 6 are constructed of an inflammable material, they may be protected from the heat within the quartz tube 5 by means of heat baiiies or reiiectors I6 positioned at each end of thequartz tube 5 between the stoppers or caps 6, and the corresponding ends of the receptacle or holder I I.

The interior of the quartz tube 5 is connected by means of a tube I'I or any other suitable connector passing through one of the Stoppers 5 to y any suitable vacuum pump, not shown, for the purpose of reducing or exhaustingthe atmosphere within the tube I. The action of the vacuum pump on the interior of the tube 5 is controlled by a valve I 8, which at the beginning of the operation, is open, and the pump is operated to reduce the pressure within the tube s to about 5 1 millimeter of mercury, which reduced pressure is maintained until the tantalum or tantalum articles are heated to from 1200" to 1400 C. by means of the heating coil 1. This pressure may be indicated by any suitable pressure indicating 10 mechanism, such as a manometer I9 connected to the tube I1, as shown in Fig. 1, and the heating of the tantalum and tantalum articles is continued until the manometer I9 indicates that substantially all of the occluded gases have been 15 driven out of the tantalum or articles being heated. When such a condition is indicated, the valve I8 is closed, disconnecting the pump from the tube 5, and a valve 2I communicating with a measuring ask 22 at one end, and with atmosphere at zo the other is opened to admit air at atmospheric pressure'to the measuring iiask 22. The valve 2| is then closed and a valve 23 is opened to admit the air in the measuring ask to the tube I'I to which the ask 22 is connected by means of a g5 tube 24 for supplying air to the interior of the quartz tube 5.l v

Thus, a measured amount or quantity of air is supplied to the quartz tube 5 and the increased pressure within the tube will be indicated by the 30 manometer I9. The heating of the tantalum or tantalum articles in the quartz tube 5 is continued until the manometer I9 indicates a return of the initial reduced pressure, whereupon the valve 23 is closed and the valve 2i opened to admit a 35 further supply of air to the measuring flask 22, which may subsequently be supplied to the interior of the quartz tube 5, as described above.

The amount of air required to produce the desired degree. of hardness, may be determined by 40 experiment and upon supplying such amount to the tantalum within the quartz tube, the valve 23 may be closed and the heating continued to properly diffuse the gas carried by the surface of the tantalum or tantalum article inwardly of the 45 tantalum to provide the hardness properties desired.

It will of course, be apparent that the measuring flask 22 communicating with the interior of the quartz tube 5 and with atmosphere, merely 50 diagrammatically illustrates one means by which it is possible to supply and control the supply of air to be absorbed by the tantalum, it being here contemplated as within the scope of the present invention to use any suitable controllable and 55 measurable source of air supply.

As already mentioned, the amount of air absorbed by the tantalum or articles made therefrom to produce the desired degree of hardness, may be determined by experiment, and I have 50 found that, in hardening a plurality of spinnerets arranged as shown in Fig. l within a quartz tube having a volume of about 2750 cubic centimeters, air may be admitted in cubic centimeter portions or quantities from time to time as the spin- 65 nerets absorb these portions of air for a period lof about one hour during which time approximately 1000 cubic centimeters of air was absorbed by the spinnerets.

I have found that about 1000 cubic centimeters 70 of air per 1000 grams of tantalum will produce a marked springiness if the heating is continued until the air is diffused throughout the metal, and that in such proportions a ille hard surface or case is formed on the tantalum if the diffusion 75 ate, the metal could be worked by rolling or swag-- ing to produce additional work hardness or to produce desirable shapes.

Illustrative of the advantages of tantalum when so hardened, I have found that tantalum spinnerets may be provided with a suitable hardness to protect the fine openings therein and noncorrosive qualities which promote durability of the spinnerets in service and 'obviate the necessity of frequently replacing such spinnerets.

While I have described the novel method as applied to tantalum, it is understood that other similar metals, such, for example, as columbum, may be treated in the same manner, and that possibly other gases, such as nitrogen, hydrogen or pure oxygen, may be substituted for air, and that I am not limited to the details as hereinabove set forth, except as defined by the following claims.

I claim:

1. A method of gas hardening a hard refractory metal from the group consisting of tantalum and columbium, by causing the hard refractory metal to absorb a hardening constituent of air, which comprises degasifying said refractory metal by heating it at a reduced pressure to from 1200 to 1400 C., supplying air to said hard refractory metal, heating said hard refractory metal to the absorbing temperature for a hardening constituent of air whereby to cause absorption thereof by said-hard refractory metal, and continuing such heating of such hard refractory metal to cause said constituent of air to` penetrate into said hard refractory metal whereby to harden it throughout.

2. A method of gas hardening tantalum, which comprises degasifying said tantalum by heating it at a reduced pressure to from 1200 to 1400 C., supplying air to said tantalum, heating said tantalum to the gas absorbing temperature for air whereby to cause absorption of the air by said tantalum,` and continuing such heating of said tantalum to cause the absorbed air to penetrate into the tantalum whereby to harden it throughout.

3. A method of gas hardening a hard refractory metal from the group consisting of tantalum` and columbium by causing it to absorb a hardening constituent of air, which comprises heating said hard refractory metal at a reduced pressure to from 1200 to 1400" C., whereby to degasify said hard refractory metal,l successively supplying predetermined quantities of air to said hard refractory metal while heating the hard refractory metal to the absorbing temperature for the hardening constituent of air until said hard refractory metal absorbs it in the proportion of about 100 cubic centimeters of the constituent of air to 100 grams of -said hard refractory metal, and con- A tinuingthev heating of said hard refractory metal with said constituent of air absorbed thereby to diffuse the absorbed constituent of air throughout said hard refractory metal. c

4. A method of gas hardening tantalum, which comprises heating said tantalum/atV a reduced pressure to from 1200 to 1400 C., whereby to degasify said tantalum, successively supplying predetermined quantities of air to said tantalum while heating the tantalum to its air absorbing temperature until said tantalum absorbs the air supplied thereto in the proportion of about 1000 cubic centimeters of air to 1000 grams of tantalum, and continuing the heating of said tantalum with the air absorbed thereby to diffuse the air throughout the tantalum.

5. A method of hardening a hard refractory metal from the group consisting of tantalum and columbium by diffusing a regulated quantity of a constituent of air through said metal, which comprises degasifying said hard refractory metal by heating it at a reduced pressure to from 1200 to 1400o C., supplying a measured quantity of air to said hard refractory metal, heating said hard refractory metal to the absorbing temperature for a hardening constituent of air whereby to cause absorption of said hardening constituent in the measured quantity of air by said hard refractory metal, continuing such heating of said hard refractory metal to cause said constituent of air to penetrate into said hard refractory metal whereby to harden it throughout, and controlling the quantity of air supplied to said refractory metal whereby to control the hardness of the resulting product.

6. A method of hardening tantalum, which comprises heating tantalum to the degasication temperature thereof in a vessel -while maintaining the atmosphere in said vessel at a pressure of about one millimeter of mercury to remove the occluded gases from the tantalum, and thereafter. simultaneously supplying air to the vessel containing the tantalum and heating said tantalum to its air absorbing temperature to cause it to absorbthe air so supplied thereto.

7. A method of hardening tantalum, which comprises heating tantalum to the degasication temperature ktlriereof in a vessel while maintaining the atmosphere in said vessel at a pressure. of about one millimeter of mercury to remove the occluded gases from the tantalum, thereafter simultaneously supplying air to the vessel containing the tantalum and heating said tantalum to its air absorbing temperature tocause it to absorb the air so supplied thereto, and dispersing the absorbed air throughout the tantalum by continuing the last mentioned heating step.

8. A hard article of manufacture, comprising tantalum and air, the air being substantially uniformly distributed throughout the tantalum in the proportion of about 1000 cubic centimeters of air to 1000 grams of tantalum.

9. An article of manufacture comprising a hard spinneret of tantalum and air, the air being subdesired hardness when the air is absorbed by the 'hard refractory metal, and heating the hard refractory metal toits air absorbing temperature to-` cause itto absorb the air so supplied thereto.

MINER ivi. AUSTIN. 

